Dataset Information

Mimicking the Self-Organized Microstructure of Tooth Enamel.

ABSTRACT: Under near-physiological pH, temperature, and ionic strength, amelogenin (Amel) accelerates hydroxyapatite (HAP) nucleation kinetics, decreasing the induction time in a concentration-dependent manner. Hierarchically organized apatite microstructures are achieved by self-assembly involving nucleated nanocrystallites and Amel oligomers and nanospheres at low supersaturations and protein concentrations in a slow and well-controlled constant composition (CC) system. The CC method allows the capture of an intermediate structure, the nanorod, following the formation of the critical nuclei at the earliest nucleation stages of calcium phosphate crystallization. The nanorod building blocks form spontaneously by synergistic interactions between flexible Amel protein assemblies and rigid calcium phosphate nanocrystallites. These intermediate structures further assemble by a self-epitaxial growth mechanism to form the final hierarchically organized microstructures that are compositionally and morphologically similar to natural enamel. This in vitro observation provides direct evidence that Amel promotes apatite crystallization and organization. We interpret our observations to propose that in vivo Amel may maximally exert an influence on the structural control of developing enamel crystals at the earliest nucleation stages.

SUBMITTER: Wang L

PROVIDER: S-EPMC2630287 | biostudies-literature | 2008 Mar

REPOSITORIES: biostudies-literature

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Mimicking the Self-Organized Microstructure of Tooth Enamel.

Wang Lijun L Guan Xiangying X Yin Haoyong H Moradian-Oldak Janet J Nancollas George H GH

The journal of physical chemistry. C, Nanomaterials and interfaces 20080301 15

Under near-physiological pH, temperature, and ionic strength, amelogenin (Amel) accelerates hydroxyapatite (HAP) nucleation kinetics, decreasing the induction time in a concentration-dependent manner. Hierarchically organized apatite microstructures are achieved by self-assembly involving nucleated nanocrystallites and Amel oligomers and nanospheres at low supersaturations and protein concentrations in a slow and well-controlled constant composition (CC) system. The CC method allows the capture ...[more]

PMID: 19169386

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Project description:Tooth enamel forms in an ephemeral protein matrix where changes in protein abundance, composition and posttranslational modifications are critical to achieve healthy enamel properties. Amelogenin (AMELX) with its splice variants is the most abundant enamel matrix protein, with only one known phosphorylation site at serine 16 shown in vitro to be critical for regulating mineralization. The phosphorylated form of AMELX stabilizes amorphous calcium phosphate, while crystalline hydroxyapatite forms in the presence of the unphosphorylated protein. While AMELX regulates mineral transitions over space and time, it is unknown whether and when un-phosphorylated amelogenin occurs during enamel mineralization. This study aims to reveal the spatiotemporal distribution of the cleavage products of the most abundant AMLEX splice variants including the full length P173, the shorter leucine-rich amelogenin protein (LRAP), and the exon 4-containing P190 in forming enamel, all within the context of the changing enamel matrix proteome during mineralization. We microsampled permanent pig molars, capturing known stages of enamel formation from both crown surface and inner enamel. Nano-LC-MS/MS proteomic analyses after tryptic digestion rendered more than 500 unique protein identifications in enamel, dentin, and bone. We mapped collagens, keratins, and proteolytic enzymes (CTSL, MMP2, MMP10) and determined distributions of P173, LRAP, and P190 products, the enamel proteins enamelin (ENAM) and ameloblastin (AMBN), and matrix-metalloprotease-20 (MMP20) and kallikrein-4 (KLK4). All enamel proteins and KLK4 were near-exclusive to enamel and in excellent agreement with published abundance levels. Phosphorylated P173 and LRAP products decreased in abundance from recently deposited matrix toward older enamel, mirrored by increasing abundances of testicular acid phosphatase (ACPT). Our results showed that hierarchical clustering analysis of secretory enamel links closely matching distributions of unphosphorylated P173 and LRAP products with ACPT and non-traditional amelogenesis proteins, many associated with enamel defects. We report higher protein diversity than previously published and Gene Ontology (GO)-defined protein functions related to the regulation of mineral formation in secretory enamel (e.g., casein α-S1, CSN1S1), immune response in erupted enamel (e.g., peptidoglycan recognition protein, PGRP), and phosphorylation. This study presents a novel approach to characterize and study functional relationships through spatiotemporal mapping of the ephemeral extracellular matrix proteome.

Dataset Information

Mimicking the Self-Organized Microstructure of Tooth Enamel.

Publications

Mimicking the Self-Organized Microstructure of Tooth Enamel.

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